Scag Tiger Cub SMTC with Briggs 26HP will not start in cold weather. The engine will not turn over fast enough to start. The dealer claims the oil viscosity is to heavy for the weather. I'm using the oil recommended by Scag. This was no problem when it was new,it started fine in the cold.This is the second season of operation .Installing a new battery didn't help. Has anyone else had this problem?